(i) Technical Field
The present invention relates to an optical semiconductor device having an optical semiconductor element having optical gain.
(ii) Related Art
A laser device (an optical semiconductor device), in which one of optical semiconductor elements having optical gain is combined with a wavelength locker including an etalon, is being known. The combination with the wavelength locker allows stabilization of output wavelength of the laser with high accuracy. Japanese Patent Application Publication No. 2001-308444 discloses such a laser.
The wavelength locker in the laser device is located on an output optical axis of the semiconductor laser. Therefore, the laser device extends in a direction along the output optical axis. There is a problem that it is difficult to downsize the laser device in which optical components such as the wavelength locker are combined.
Especially, a chip length of a wavelength tunable laser, in which a SG-DBR (Sampled Grating Distributed Bragg Reflector), a SG-DFB (Sampled Grating Distributed Feedback), and so on are coupled, may be large. There is a problem that it is difficult to downsize the laser device having the wavelength tunable laser.